KPESCEPHALOX 



715 



Tlic inferior surface of the cerebellum shows a pronounced convexity corre- 

 sponding to the inferior fossic of the occipital bone on which it rests. It is smoothly 

 rounded off externally and behind, but changes its direction abruptly internally and 

 in front, where it conies in contact with the medulla and pons. It is marked off 

 into lol)es, which are arranged in the following order from Ijehind forwards: i»ns- 

 terior inferior, slender, l>iventral, tonsillar, and Hocculus. The posterior inferior 

 is a narrow crescentic lolic, wliich l)ounds the great horizontal fissure inferiorly. 

 The slender (lobulus gracilis) is similar in shape, l»ut narrower, as its name 

 implies. The biventral, sliorter and thicker than the two last described, is divided 

 by a well-marked fissure into an anterior and a posterior portion. The tonsillar 

 lobe (amygdala) lies internal and slightly anterior to the biventral, and is partly 

 hidden in the vallecula. The flocculus is a small lobe forming a marked projec- 

 tion in front of the biventral lobe, which it separates from the middle peduncle of 

 the cerebellum. 



The inferior vermiform process is formed by the following parts, taken in 

 order from behind forwards: tuber valvuhe, pyramid, uvula, and nodule. The 

 tuber valvulae is a transverse l)and, consisting of about seven or eight folia, which 

 connects the posterior inferior and slender lobes with their fellows of the opposite 



Fig. 426. — Inferior Surface of the Cerebellum. 

 (From a mounted specimen in the Anatomical Department of Trinity College, Dublin. 

 VALVE OF VIEUSSENS LOBVLUS CENTRALIS 



MIDDLE 

 PEDUNCLE 

 FLOCCUL 

 FOURTH 

 VENTRICLE 

 BIVENTRAL 

 LOBE 



UVULA 



PYRAMID 



SLENDER 



LOBE 



POSTERIOR 



INFERIOR 



LOBE 



SUPERIOR PEDUNCLE 



POSTERIOR 

 CRE.SCENTIC 

 LOBULE 



SULCUS 

 CEREBELLI 

 > I PERIOR 



VOD ULE 

 IMYGDALA 



TUBER 



VALVULJE 



I NCI SURA 

 MARSUPIALIS 



side. The pyramid is the most massive portion of the inferior vermiform process, 

 and is connected to the l)iventral lobes on each side. It consists of from five to 

 eight folia. The uvula is an elongated portion, compressed laterally, and connected 

 to the amygdala on each side by the furrowed band. The nodule, or laminated 

 tubercle, is the prominent anterior extremit}' of the inferior vermiform process 

 which projects into the cavity of the fourth ventricle. It is connected to the floc- 

 culus on each side by a thin white plate, the inferior medullary velum. The 

 latter will be referred to in connection with the anatomy of the fourth ventricle. 



Dissection. — The student should now obtain a view of the principal systems of fibres in the 

 cerebelhim by the following dissection, which we shall speak of as Reil's metliod. The great 

 horizontal fissure should be opened up and the portion of the cerebellum which lies superior to 

 that fissure gently torn off the underlying portion. If this proceeding has been successfully 

 accomplished, a large bundle of fibres will be seen passing through a gap between the superior 

 and middli' jieduncies of the cerebellum, and ])assing towards the superior surface. This bundle 

 is formed by the restiform body and by tlie lower fibres of the pons. The ]iosition of the corpus 

 dentatum will also be noticeable near tlie middle line, as the white fibres which form the capsule 

 of that body are disposed in ridges corresponding to the plications of grey matter of the 

 nucleus. A more superficial dissection on the opposite side will show the fibres of the above- 

 mentioned bundle passing inwards, forming at first curves convex backwards, and then sweeping 

 upwards into the folia of the superior vermis. A li(jrizontal section through tlie corpus dentatum 



